[Reprinted  from  The  Psychological  Review,  Vol.  27,  No.  6,  November,  1920.I 


A  BEHAVIORISTIC  ACCOUNT  OF  SLEEP 

BY  CHARLES  H.  WOOLBERT 

Division  of  Public  Speaking,  University  of  Illinois 

The  phenomenon  of  sleep  does  not  lend  itself  conveniently 
to  explanation  in  terms  of  sensation,  image,  and  feeling. 
Accordingly  structural  psychology  can  offer  little  by  way  of  a 
description  of  the  state  of  sleep.  The  behaviorist,  on  the 
other  hand,  believing  that  his  definition  of  consciousness 
offers  a  statement  not  only  of  what  consciousness  is,  but  of 
what  it  is  not,  is  in  a  position  to  explain  sleep.  If,  as  be¬ 
haviorism  asserts,  mind  is  a  matter  of  reflex  connections  always 
involving  the  movement,  tension,  or  tonicity  of  muscles  and 
always  correlated  with  the  activity  of  glands,  then  conscious¬ 
ness,  in  its  varying  degrees  of  clearness,  is  a  matter  of  degrees 
of  complexity  and  ordination  among  systems  of  muscular 
action.  A  high  degree  of  consciousness  thus  becomes  synony¬ 
mous  with  an  intricate  and  ordered  complexity  of  tonicity  in 
muscular  systems;  while  a  low  degree  of  consciousness  is 
equivalent  to  a  complexity  of  low  degree  and  an  ordering  of 
simple  texture.  Consciousness  thus  may  be,  speaking  in  a 
paradox,  scattered,  involving  perchance  abundant  activity — 
by  way  of  muscular  tonus  in  various  muscle  systems — but 
activity  of  a  low  degree  of  intricacy  in  organization. 

If  consciousness,  then,  be  a  matter  of  the  degree  of  com¬ 
plexity  of  interacting  muscle  systems,  non-consciousness  is  a 
lack  of  activity  or  else  a  lack  of  this  complexity.  In  either 
case  the  factor  of  complexity  is  vital  and  needs  describing. 
Behaviorism’s  explanation  of  this  concept  is  based  on  the 
continuative  function  of  the  sense  endings  within  the  muscles. 
Always  stimulated  by  any  muscular  event,  they  afford  the 
means  for  causing  a  single  inaugurating  stimulation  to  rever¬ 
berate  through  a  long  series  of  tensions,  or  else  to  provide  a 
continued  hardening  of  some  one  set  of  muscles.  The  type 
of  tensions  running  in  a  series  is  what  is  called  the  chain 

420 


A  BEHAVIORISTIC  ACCOUNT  OF  SLEEP 


A  BEHAVIORISTIC  ACCOUNT  OF  SLEEP  42 1 

reflex;  the  continued  is  that  called  circular.  Chain  reflexes 
have  much  to  do  with  that  complexity  of  interacting  muscle 
systems  that  makes  consciousness.  Carried  on  by  means  of 
proprioceptor  organs  of  stimulation,  they  have  a  right  of  way 
and  a  special  kind  of  clearance.  This  insures  them  continuity 
and  lends  a  measurable  degree  of  stability  to  the  complexity 
of  structure  that  makes  up  consciousness. 

This  description  recognizes,  first,  that  the  muscularity  of 
the  body  occurs  in  fairly  well-defined  systems:  as  those  of 
the  back,  the  legs,  the  head,  the  face,  and  the  throat;  and, 
secondly,  that  these  muscle  systems  are  set  oflF  one  by  the 
other  and  in  a  certain  order.  This  order  is  based  on  priority. 
Priority  of  muscle  systems  is,  in  general,  a  matter  of  pre¬ 
cedence  in  the  development  of  working  efficiency  in  reflex 
arcs.  Those  systems  that  have  an  early  development  history 
come  to  have  a  pronounced  control  over  systems  developed 
later,  in  that  the  systems  developed  later  get  their  initial 
determinations  from  the  workings  of  the  habitual  responses 
of  the  earlier.  Their  most  intense  determinations  are,  both 
earlier  and  later,  then,  conditioned  by  the  determinations  of 
the  systems  already  habituated.  Their  capacity  for  quick 
and  valuable  response  depends  thus  very  largely  upon  their 
close  coordination  and  cooperation  with  habitual  reactions 
of  systems  determined  at  an  earlier  stage  of  development. 

An  understanding  of  sleep  requires  a  description  of  this 
development  order,  a  description  of  gross  muscle  systems 
and  a  statement  of  their  superordination  and  subordination. 
This  is  found  in  an  account  of  the  operation  of  Pawlow’s- 

A 

Law,  as  manifested  in  the  conditioned,  chain,  and  circular 
reflexes. 

By  Pawlow’s  Law  a  reflex  arc  may  be  a  factor  in  new 
activities  by  the  stimulation  of  sense  endings  imbedded  in  the 
muscles  that  are  contracted  by  the  operation  of  such  an  arc. 
Every  motor  process  stirs  a  muscle;  this  stirring  starts  new 
impulses;  and  these  impulses  seek  a  new  outlet.  Two  direc¬ 
tions  they  can  take:  they  can  go  around  back  by  way  of  the 
motor  nerve  that  stimulates  this  muscle,  and  so  stimulate  it 
again;  or  they  can  take  some  other  motor  nerve  leading  to  a 


OF  ILtir^CIG 
AT  URHAMA-CHArr  AIQM 


422 


CHARLES  H.  WOOLBERT 


quite  different  muscle.  The  former  of  these  processes  is  the 
circular  reflex,  the  latter,  when  carried  on  through  a  series, 
the  chain  reflex.  By  means  of  circular  and  chain  reflexes  in 
various  combinations  the  organism  has  within  itself  the 
machinery  for  carrying  on  activity,  for  a  while,  at  least, 
without  the  intervention  of  peripheral  stimulations.  Only  in 
this  way  can  the  continued  activity  of  involuntary  organic 
acts  be  accounted  for,  activities  like  heart-beat  and  breathing. 
In  this  way  also  is  given  a  satisfactory  account  of  the  mechan¬ 
ism  of  such  activities  as  catatonia,  catalepsy,  emotional  com¬ 
plexes,  fixed  ideation — in  fact,  repetitive  and  continuative 
actions  of  all  kinds. 

To  get  the  full  significance  of  these  circular  and  chain 
reflex  systems  in  the  coordination  and  superordination  of 
actions,  it  is  necessary  to  envisage  them  in  connection  with 
the  development  order  of  muscular  systems.  Systems  de¬ 
veloped  early  in  the  life  of  the  organism  are  obviously  deter¬ 
mined  strongly;  in  the  case  of  the  very  earliest,  heart-beat 
and  breathing,  no  stimulus  short  of  that  adequate  to  stop 
life  can  divert  them.  Moreover,  their  continued  activity  is 
but  little  dependent  upon  other  stimulation  than  that  pro¬ 
vided  by  the  circular  reflexes  that  keep  them  regular;  at 
least  so  long  as  the  muscles  concerned  receive  nourishment 
from  the  blood.  Systems  developed  one  stage  later,  like 
those  involving  walking,  reaching,  turning  the  head,  have 
within  themselves  much  of  the  same  continuative  mechanism. 
Their  ability  to  function,  however,  they  have  gained  largely 
as  an  adjustment  from  the  successful  functioning  of  systems 
developed  earlier.  At  the  start  of  their  functioning  they  do 
not  possess  a  full  measure  of  self-determination;  they  are  of 
necessity  dependencies,  subject  to  the  caprice  of  superiors 
holding  power  by  a  rule  of  seniority.  Certain  things  they 
can  do  so  long  as  the  older  systems  go  about  their  business 
in  an  orderly  fashion;  certain  other  things,  under  the  same 
conditions,  they  are  not  privileged  to  attempt.  Thus  the 
use  of  the  eyes,  the  hands,  the  legs,  is  conditioned  very 
materially  by  the  regularity  of  the  beating  of  the  heart  and 
of  breathing.  Let,  once,  something  go  wrong  with  either  of 


A  BEHAVIORISTIC  ACCOUNT  OF  SLEEP 


423 


these  older  activities,  and  the  organism  loses  complete  control, 
eventually,  of  hands,  legs,  eyes,  and  of  all  other  muscle 
systems.  Under  similar  circumstances  any  determinations 
that  are  ordinarily  well  established  give  way  to  a  recrudes¬ 
cence  of  the  wildest  of  random  movement. 

Thus  the  muscle  systems  operate  in  a  kind  of  hierarchy, 
with  jurisdictions  fairly  distinct,  though  not  exclusive.  Most 
firmly  enthroned  of  all  are  the  primary  reflex  systems  con¬ 
trolling  heart-beat,  flow  of  blood,  operation  of  vital  organs, 
and  breathing.  Next  come  those  developed  in  the  organism’s 
earlier  days,  use  of  arms  and  legs,  back,  torso,  and  neck 
muscles;  later,  and  probably  overlapping  the  earlier  systems, 
muscles  of  the  eyes,  ears,  face,  and  head;  lastly — coincident 
with  the  development  of  speech — the  muscles  of. jaws,  lips, 
tongue,  and  throat.  Thus  consciousness  as  complexity  of 
muscle  systems  is  a  pyramid  with  the  organic  systems  at  the 
base  and  the  muscles  of  thinking,  reasoning,  and  speech  at  the 
top.  Or,  changing  the  figure,  it  is  a  hierarchy  with  the 
organic  systems  as  autocrats  and  the  other  systems  holding 
office  on  a  descending  scale  of  self-government,  dependent 
always  upon  the  commands  of  the  autocrats  ruling  by  virtue 
of  prior  possession  of  power. 

This  hierarchy  operates  to  provide  the  difference  between 
sleep  and  waking  consciousness.  Without  the  tension  of  head 
and  face  systems  there  is  not  complexity  enough  for  conscious¬ 
ness.  So  vital  are  they  to  clear  cognition  that  they  are 
easily  confused  with  the  totality  of  consciousness;  remove 
them  altogether  from  the  systems  active  at  any  one  time,  and 
unconsciousness  occurs.  Yet  they  are  not  autonomous ;  when 
fatigued  and  free  from  intense  peripheral  stimulation  they 
normally  yield  easily  to  the  relaxing  of  the  lower  systems  and 
go  out  of  function  along  with  them.  Any  condition  in  which 
they  refuse  to  stop  functioning  when  free  from  peripheral 
stimulation  or  when  fatigued,  and  when  the  lower  systems 
have  relaxed,  is  looked  upon  as  abnormal.  In  fact  psycho¬ 
pathic  conditions  can  be  described  either  in  terms  of  an 
actual  lack  of  the  upper  systems,  or  in  terms  of  their  failure  to 
cooperate  with  the  activities  of  the  lower.  Sleep  is  accounted 


424 


CHARLES  H.  WOOLBERT 


for  in  the  formula:  Remove  the  higher  systems  from  activity, 
and  consciousness  departs  altogether;  weaken  the  lower,  and 
consciousness  is  in  a  precarious  condition,  especially  if  the 
higher  systems  are  affected  by  fatigue.  When  the  lower 
systems  are  thrown  out  of  function,  the  higher  circular  reflexes 
either  stop  at  once  or,  in  abnormal  cases,  ultimately  wear 
themselves  out;  in  either  case  consciousness  breaks  up. 
Remove  the  lower  entirely,  and  death  is  instantaneous. 

A  prime  requisite  of  easy  and  deep  sleep  is  freedom  from 
stimulation  for  the  eye,  ear,  nose,  tongue,  and  parts  of  the 
skin  not  constantly  pressed  by  clothes;  forms  of  stimulation 
that  have  little  to  do  with  the  organic  systems.  Yet  sleep  is 
possible  even  in  the  face  of  such  stimulations;  but  only  in 
cases  where  great  fatigue  throws  lower  systems,  like  those  of 
leg  muscles,  back,  and  neck,  out  of  commission.  The  chief 
power  of  estopping  other  systems,  especially  under  conditions 
when  fatigue  is  present,  is  authoritatively  appointed  to  the 
organic  systems;  because  they  get  their  determination  at  a 
time  when  the  organism  is  in  its  most  plastic  state — in  its 
early  stages. 

Thus  sleep  becomes  behavioristically  a  matter  of  the 
efficient  domination  of  the  upper  systems  by  the  lower, 
operating  through  the  relaxing  power  of  fatigue;  while  wake¬ 
fulness  and  insomnia  always  imply  that  the  higher  and  later 
systems  are  assuming  dominance  over  their  precursors. 
Wakefulness,  so,  is  characteristically  the  dominance  of  the 
lower  systems  by  the  upper  when  fatigue  is  not  present. 
Accordingly  when  wakefulness  exists  at  the  same  time  that 
fatigue  is  present,  the  condition  is  abnormal. 

This  means  that  when  the  muscles  of  the  back,  legs,  and 
neck  are  relaxed,  a  powerful  stimulator  is  lost  to  the  muscles 
of  the  arms,  hands,  feet,  and  head.  When  arms,  hands,  feet, 
and  head  muscles  in  turn  are  relaxed,  there  is  lost  a  powerful 
source  of  stimulation  to  the  muscles  of  the  face,  jaw,  tongue, 
and  throat.  While  systems  are  undoubtedly  more  finely 
differentiated  than  this,  still  their  hierarchical  interdependence 
is  on  just  such  an  order — and  sleep  can  be  explained  by  gross 
characterizations  as  well  as  by  those  more  minute.  In  the 


A  BEHAVIORISTIC  ACCOUNT  OF  SLEEP 


425 


inducing  of  sleep  much  significance  must  be  attached  to  the 
order  in  which  muscle  systems  go  out  of  function.  When  the 
organism  follows  the  development  sequence,  sleep  is  easy; 
when  the  order  of  relaxation  is  in  any  way  reversed,  restless¬ 
ness  and  wakefulness  follow.  In  cases  of  complete  reversal 
of  the  order,  we  get  such  states  as  hypnosis,  temporary  high 
degress  of  attention,  manic  conditions,  and  forms  of  insanity. 

The  beginning  of  sleep  then  normally  is  the  relaxation  of 
the  muscles  that  hold  the  body  erect.  As  soon  as  these 
muscles  are  relaxed,  the  prime  determiner  of  higher  systems 
is  taken  away,  the  proprio-ceptor  foundation,  and  the  higher 
systems  then  are  kept  in  function  by  only  a  veritable  bom¬ 
bardment  from  the  outside  world  or  from  very  strongly  deter-  . 
mined  circular  or  chain  reflex  arcs  within  their  own  system,  j 
Among  these  latter  are  emotional  states,  fixed  ideas,  tunes  ,  ** 
running  through  the  head,  repeated  attempts  to  solve  a|y 
problem,  rhythmical  verbalizing,  and  thinking  in  circles. 

The  next  step  in  normal  sleep  is  the  sequential  relaxation 
of  each  of  the  systems  hierarchically  dependent  upon  the 
erect-holding  systems.  Finally  through  the  sufficient  dissolu¬ 
tion  of  the  complexity  that  makes  consciousness,  sleep  comes. 
Consequently  once  a  person  lies  down,  relaxing  the  muscles 
of  legs,  back,  and  neck,  the  beginning  is  made  of  sleep. 
Providing  there  is  no  interference  from  outside  stimulations — 
chiefly  those  acting  upon  the  sense  endings  in  the  head — and 
also  so  long  as  there  is  no  intense  circular  reflex  process 
going  on  in  the  muscles  of  the  jaw,  lips,  tongue,  or  throat, — 
‘thoughts  that  will  not  go  out  of  one’s  head’ —  such  a  be¬ 
ginning  once  made  leads  to  complete  sleep  and  loss  of  con¬ 
sciousness. 

Certain  easily-made  empirical  observations  as  to  sleep 
confirm  this  account,  (i)  Sleep  is  characteristically  accom¬ 
panied  by  relaxation  of  muscles.  (2)  Characteristically  also 
it  takes  place  with  the  body  in  a  horizontal  position,  a  position 
that  induces  first  of  all  a  relaxation  of  the  muscles  of  the  legs, 
back,  and  neck,  all  of  which  must  maintain  a  high  degree  of 
tonicity  to  maintain  erect  posture.  (3)  When  the  muscles 
of  the  back,  legs,  and  neck  are  relaxed,  the  muscles  of  the 


426 


CHARLES  H.  WOOLS ERT 


head,  face,  jaw,  and  throat  all  tend  to  relax  in  a  short  time 
ensuing.  (4)  These  muscles  also  are  most  easily  relaxed 
when  freed  from  stimulation  of  the  head  sense  endings,  in  the 
dark  and  in  silence  and  free  from  intense  taste  or  smell.  (5) 
All  these  relaxations  occur  parallel  with  a  scattering  of  con¬ 
sciousness,  a  defocalizing  of  attention;  and  the  greater  the 
degree  of  relaxation,  the  less  the  ability  to  perform  any  act 
implying  a  high  degree  of  concentration.  (6)  Organic  activi¬ 
ties,  though,  are  kept  up  despite  any  relaxation  of  the  volun¬ 
tary  muscle  systems.  (7)  Again,  deep  sleep  implies  complete 
relaxation;  also  it  connotes  rest  and  recuperation  from 
fatigue,  a  retoning  of  muscles  for  future  work.  (8)  The 
degree  of  sleep  involved  conditions  the  number  and  vividness 
of  dreams  had;  deep  sleep  implying  few  dreams  and  light; 
light  sleep  implying  many  dreams  or  dreams  that  are  vivid. 
(9)  Deep  sleep  also  leaves  little  recollection  of  dreams,  except 
for  the  moment  when  one  is  coming  out  of  sleep  to  conscious¬ 
ness.  (10)  Great  numbers  of  dreams,  or  dreams  that  are 
vivid,  it  is  generally  assumed,  are  equivalent  to  defective  rest, 
and  restlessness  is  always  accompanied  by  the  inability  to 
stop  thinking  or  by  numerous  and  intense  dreams,  (ii) 
During  widespread  muscular  activity  there  is  no  such  thing 
as  sleep;  as  during  walking,  eating,  reading,  talking,  giving 
active  attention  in  any  way. 

These  general  observations,  and  many  others  of  similar 
nature,  point  clearly  to  the  close  relation  existing  between 
sleep  and  the  movement  or  tonicity  of  muscles. 

In  the  subjective  terms  of  ideation,  sensation,  and  feeling 
it  is  difficult  to  explain  what  happens  to  conceptual  thought 
during  sleep.  The  behaviorist,  by  assuming  that  thought 
of  all  kinds  and  in  all  degrees  is  a  matter  of  muscular  tonus, 
precisely  as  in  walking  or  standing  erect  or  moving  the  hands 
or  talking,  can  give  an  account  of  sleep  that  fits  in  with  his 
whole  program.  Sleep  to  him  is  nothing  but  a  disorganiza¬ 
tion  of  muscle  systems  which  in  waking  consciousness  are 
closely  interrelated  hierarchically,  the  action  of  each  deter¬ 
mined  in  part  by  the  continued  action  of  the  others.  When 
conditions  are  set  for  the  relaxation  of  sundry  systems  of 


A  BEHAVIORISTIC  ACCOUNT  OF  SLEEP 


427 


muscles,  consciousness  begins  to  be  more  scattered,  system 
after  system  drops  out  of  function,  and  ultimately,  in  the 
soundest  sleep,  nothing  is  left  by  way  of  muscular  activity 
but  the  functioning  of  the  organic  systems. 

Dreams  are  clearly  the  result  of  systems  involving  throat, 
face,  tongue,  and  lip  muscles  which  remain  in  function  when 
other  systems  have  been  thrown  out  of  gear,  systems  which,  if 
combined,  would  make  consciousness.  The  Freudian  dream 
psychology  presents  agreement  with  obvious  facts  in  that  it 
recognizes  the  existence  during  sleep  of  mental  processes 
which  seem  very  like  others  that  go  on  in  waking  conscious¬ 
ness,  yet  which  at  the  same  time  are  partly  unlike  them. 
The  behavioristic  explanation  of  this  is  that  in  so  far  as  a 
dream  is  a  matter  of  the  activity  of  muscle  systems  involving 
a  high  degree  of  complexity  and  coordination,  in  so  far  it  is 
similar  to  waking  consciousness;  and  so  has  a  way  of  seeming 
logically  coherent.  The  illogical  dream,  on  the  other  hand, 
the  freakish  dream,  the  dream  that  seems  to  forbid  explana¬ 
tion  and  interpretation,  can  be  explained  broadly  as  a  type 
of  organization  and  coordination  not  met  with  in  that  form 
in  waking  life;  so  that,  speaking  generally,  the  more  unusual 
the  combination  left  operative  during  sleep,  the  more  fan¬ 
tastic  the  dream.  From  these  suppositions  can  also  be  found 
the  reason  why  dream  analysis  cannot  be  a  matter  of  accurate 
interpretation  and  why  the  Freudians  who  assume  to  inter¬ 
pret  all  dreams  give  promises  in  reality  beyond  powers  of 
observation  to  fulfill.  So  entirely  beyond  inspection  and 
prediction  can  be  the  permutations  and  combinations  of  the 
hierarchy  of  muscle  systems,  that  they  can  defy  all  powers 
of  analysis. 

From  these  observations  follow  certain  therapeutic  in¬ 
ferences  worthy  of  note,  most  of  them  current  already  through 
the  experience  of  the  race.  If  you  would  sleep  soundly,  exer¬ 
cise  much,  in  particular  the  muscle  systems  of  the  body  below 
the  head;  for  if  the  ‘body’  is  tired,  the  ‘mind’  will  rest  also. 
If  restless  in  sleep,  study  how  to  relax,  first  of  all  the  muscles 
of  the  legs,  back,  and  neck.  Then  reduce  the  breathing  rate: 
high  tension  almost  invariably  is  accompanied  by  rapid  breath- 


428 


CHARLES  H.  WOOLBERT 


ing;  low  tension  by  slow-breathing.  Also  hands  and  feet, 
fingers  and  toes,  must  be  inert.  If  thoughts  crowd  thick 
and  fast  and  will  not  leave,  let  the  jaw  drop,  make  the 
muscles  of  the  cheeks  and  lips  flabby,  avoid  screwing  up 
the  muscles  around  the  forehead  and  the  eyes,  see  that  the 
tongue  lies  limp  in  the  mouth,  and  make  certain  that  the 
muscles  of  the  throat  are  not  in  any  way  tensed.  These 
last-named  muscles,  together  with  those  of  the  jaw,  tongue, 
and  lips,  are  more  likely  than  any  other  to  get  in  the  way  of 
sound  sleep.  Make  sure  to  observe  the  right  order  of  relaxa¬ 
tion  of  systems;  gross  lower  systems  first,  then  the  finer  sys¬ 
tems  below  the  head,  and  finally  the  fine  systems  of  the  head. 
Sleep  is  synonymous  with  carrying  out  the  following  order 
in  relaxation:  Reduce  the  breathing  rate;  then  relax  legs, 
back,  abdomen,  and  neck;  then  arms,  hands,  fingers,  and 
toes;  next  the  muscles  around  the  eyes,  forehead,  scalp,  and 
ears;  and  finally  those  around  the  mouth,  jaws,  tongue,  and 
throat — the  muscles  of  speech  and  conceptual  thought. 


